The current BiS suggestions show gear from Tomb of Sargeras, which is not available at the moment.
How can I “rollback” BiS to provide suggestions for current Nighthold content, which should be relevant for a few more months?

My goal is to build a BiS list for Nighthold that is based around the legendaries I actually have.

In the filters menu, you can turn off the Tomb of Sargeras gear. Here’s a blog post that shows you were the filters are (I don’t have the screenshots updated for ToS gear, but you get the idea). http://blog.askmrrobot.com/filters-gear-lists/